Method for enhancing magnetic properties of rare earth permanent magnets

Abstract

A method for treating rare earth permanent magnetic material is disclosed. The treatment includes soaking ribbon rare earth permanent magnetic material consisting essentially of grains of the tetragonal crystal phase RE 2 TM 14 B where RE is neodymium and/or praseodymium or mixtures thereof with other rare earth elements and TM is iron or mixtures of iron and cobalt, cobalt in a soaking solution of either distilled water or phosphoric acid and manganese phosphate solution, draining off the soaking solution, rinsing with distilled water while agitating to separate and remove fine powdered magnetic material, and washing and drying the remaining powder or ribbons. The treated material is taken to substantial dryness before the material is incorporated into a permanent magnet.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. In the process of making permanent magnets by melt spinning a molten iron-rare earth element-boron containing composition to form particles having a crystal grain size no greater than about 500 nanometers and subsequently bonding or pressing the material into a permanent magnet body, the permanent magnet body consisting essentially of grains of the tetragonal crystal phase RE 2  TM 14  B where RE is neodymium and/or praseodymium or mixtures thereof with other rare earth elements and TM is iron or mixtures of iron and cobalt, the improvement comprising: soaking rare earth permanent magnetic material in distilled water;   draining off the soaking water and rinsing the magnetic material with more distilled water while agitating to separate the magnetic material into a first, heavier portion and a second, less dense portion by allowing the first heavier portion of the magnetic material to sink to the bottom of the container while allowing the second, lighter portion of the magnetic portion to float on top of the water rinse;   draining off the rinse water and the floating portion; and   drying the remaining heavier portion of the treated magnetic material to substantial dryness.   
     
     
       2. The process of claim 1, wherein said soaking step is accomplished by soaking the magnetic material for about 15 minutes. 
     
     
       3. The process of claim 1, wherein said draining and rinsing step is repeated from about 2 to about 10 times. 
     
     
       4. The process of claim 1, wherein said drying step is accomplished by air drying. 
     
     
       5. In the process of making permanent magnets by melt spinning a molten iron-rare earth element-boron containing composition to form particles having a crystal grain size no greater than about 500 nanometers and subsequently bonding or pressing the material into a permanent magnet body, the permanent magnet body consisting essentially of grains of the tetragonal crystal phase RE 2  TM 14  B where RE is neodymium and/or praseodymium or mixtures thereof with other rare earth elements and TM is iron or mixtures of iron and cobalt, the improvement comprising: soaking rare earth permanent magnetic material in a solution containing phosphoric acid and manganese phosphate;   draining off the soaking solution;   rinsing the soaked magnetic material with distilled water while agitating to separate the magnetic material into a first heavier portion and a second, less dense portion by allowing the first heavier portion of the magnetic material to sink to the bottom of the container while allowing the second, less dense portion of the magnetic material to float on top of the water rinse;   draining off the rinse water and the floating portion; and   drying the remaining heavier portion of the treated magnetic material to substantial dryness.   
     
     
       6. The process of claim 5, wherein said soaking step is accomplished by soaking the magnetic material for about 3 to about 15 minutes. 
     
     
       7. The process of claim 5, wherein said draining and rinsing step is repeated from about 2 to about 10 times. 
     
     
       8. The process of claim 5, wherein said drying step is accomplished by air drying. 
     
     
       9. In the process of making permanent magnets by melt spinning a molten iron-rare earth element-boron containing composition to form particles having a crystal grain size no greater than about 500 nanometers and subsequently bonding or pressing the material into a permanent magnet body, the permanent magnet body consisting essentially of grains of the tetragonal crystal phase RE 2  TM 14  B where RE is neodymium and/or praseodymium or mixtures thereof with other rare earth elements and TM is iron or mixtures of iron and cobalt, the improvement comprising: immersing the rare earth permanent magnetic material in a soaking solution containing chemical compounds selected from the group consisting of distilled water, manganese phosphate, phosphoric acid and mixtures thereof;   draining off the soaking solution;   rinsing the magnetic material with distilled water while agitating to separate the magnetic material into a first heavier portion which sinks to the bottom of the container, and a second, less dense portion which floats on top of the rinse water;   draining off the rinse water and the floating portion;   repeating the rinsing and draining steps from about 2 to about 10 times; and   drying the first, heavier portion of the treated magnetic material to substantial dryness.   
     
     
       10. The process of claim 9, wherein said immersing step is accomplished by soaking the magnetic material from about 3 to about 15 minutes. 
     
     
       11. The process of claim 9, wherein said drying step is accomplished by air drying. 
     
     
       12. In the process of making permanent magnets by melt spinning a molten iron-rare earth element-boron containing composition to form particles having a crystal grain size no greater than about 500 nanometers and subsequently bonding or pressing the material into a permanent magnet body, the permanent magnet body consisting essentially of grains of the tetragonal crystal phase RE 2  TM 14  B where RE is neodymium and/or praseodymium or mixtures thereof with other rare earth elements and TM is iron or mixtures of iron and cobalt, the improvement comprising: immersing powdered rare earth permanent magnetic material in a phosphoric acid and manganese phosphate soaking solution;   draining off the soaking solution;   rinsing the magnetic material with distilled water while agitating to separate the magnetic material into a first heavier portion consisting of magnetic material particles which sink to the bottom of the container and a second, less dense portion of very fine particles of less than about 200 mesh size which float to the top of the rinse water;   draining off the rinse water and the floating fine particles of the powdered magnetic material on the top of the rinse water;   repeating the steps of rinsing and draining from about 2 to 10 times until there is a diminishing number of very fine particles floating on the rinse water surface; and   air drying the first, heavier portion of the magnetic material to substantial dryness.